DDH, Bony birth Canal, PAO, 3D-CT, Maximum-inscribed-sphere, Orthopedic surgery, RD701-811, Diseases of the musculoskeletal system, RC925-935

Abstract Background To explore the application of a new three-dimensional computed tomography measurement (maximum-inscribed-sphere method) in female DDH (developmental dysplasia of the hip) patients with gynecoid and anthropoid type pelvis on measuring the bony birth canal before and after unilateral PAO (periacetabular osteotomy). Methods A total of 19 female DDH patients of childbearing age were included in this study. The pelvis types were classified as gynecoid (11 patients) and anthropoid (8 patients). The maximum-inscribed-sphere method was applied to measure the bony birth canal. The lateral central edge angle (LCE), the anterior central edge angle (ACE), the Tönnis angle, and the distance between the femoral head and Koher’s line were measured. Results For the gynecoid type, the narrowest part of the bony birth canal before and after the surgery occurred both at the 21st layer of bilateral ischial spines and the 4th sacrum (107.39 mm ± 4.33 mm; 106.27 mm ± 4.76 mm). In anthropoid patients, the narrowest part of the bony birth canal was found at the 21st layer before surgery (105.89 mm ± 6.58 mm), and the 19th layer after surgery (103.48 mm ± 7.36 mm). The most significant narrowing was found at the 8th layer (4.25 mm ± 3.51 mm p